Templates Assisted Preparation Of ZnO Micro/Nanostructures

Using templates to control the size, morphology, structure and arrangement of ZnO micro-nano structures is of great significance in preparations and applications of ZnO micro/nano-devices.In this thesis, we synthesized well-aligned ZnO nanorod arrays by hydrothermal method on Si substrates that were covered with pre-deposited ZnO films as seed layers. The ZnO seed layers were deposited by RF magnetron sputtering. We explored the effect of sputtering parameters of seed layers such as oxygen partial pressure and annealing on the morphology of ZnO nanorod arrays. To the very best of our knowledge, these works have seldom been done before. By adjusting the precursor concentration, or adding different capping agents like sodium citrate and polyethylenimine(PEI), aliened ZnO nanrod/towe/wire arrays with different morphologies and aspect ratios were successfully synthesized.Besides, by patterning photoresist layer on the surface of seed layers via conventional lithography, a simple aqueous solution route was demonstrated to control the growth positions of ZnO micro/nanno-structure arrays on the substrates. Through adjusting the growth parameters, periodic ZnO nanorod/tubes/wire/circular arrays were prepared with the assist of photoresist templates.Furthermore, under the functions of capping agents like citrate and polyethylenimine (PEI), two kinds of organic molecules that could hinder the axial and lateral growth of the nanorod and separating the growth process into two steps, multi grains within one photoresist hole fused together into single crystal with restriction of photoresist template. For the first time, it is possible to define the position of single oriented one dimensional ZnO crystal on polycrystalline substrates instead of expensive single crystal substrates at low temperatures and large scale. The size of template to control the growth position of single ZnO nanorods has been extended from 100nm that literature generally reported to the range of micrometer. A crystal growth mechanism was proposed when growing under the functions of photoresist templates and capping agents.With restriction of photoresist templates, the diameters of nanorods were enlarged to the size of photoresist holes under the same hydrothermal growth conditions, the prepared ZnO one dementional structures have controlled diameters and lengths.At last, ordered ZnO nanobowl arrays over cm2 areas were prepared by magnetron sputtering using the self-assembled colloidal crystals as templates. The process started with self-assembled sedimentation of there-dimensional (3D) hexagonal polystyrene sphere arrays. By depositing ZnO within the interstitials of 3D colloidal crystal templates using magnetron sputtering, large-area ordered ZnO nanobowl sheets were prepared after removing the spheres by annealing. The whole nanobowl sheet could be lifted off, leaving accidentally observed inverse opal structures. The sizes of the nanobowls could be controlled by the size of the polystyrene spheres, the height of nanobowl sheets could be altered by changing sputtering parameters.